In recent years, an optical equipment used for medicine has been developed variously to a high degree. Especially in ophthalmology, the optical equipment becomes widespread as an optical characteristic measuring apparatus for testing an eye function, such as refraction of an eye or adjustment thereof, and the inside of an eye. In the measurement results of these various tests, it becomes important that for example, a patient's eye to be measured as a test object is put in what decision factor for measuring timing.
Besides, in general, corneal topography is effective in many uses, for example, prediction of results of a surgical operation such as keratotomy or keratectomy, clinic after corneal transplant, design and evaluation of contact lenses for shortsightedness or farsightedness, diagnosis of a cornea and judgment of a disease thereof, and the like. As a conventional measuring method of a corneal shape, there is, for example, a Placido disk technique, a stereoscopic photography technique, a moire technique, a topography interference technique or the like.
As the optical characteristic measuring apparatus, for example, there is known an apparatus in which a point light source is projected on a retina and is converted into a predetermined number of beams by a conversion member such as a Hartmann plate, and the beams are received by a light receiving part to measure the optical characteristic of the eye, or a corneal shape measuring apparatus in which a Placido's disk with visible light is used to measure the corneal shape. Incidentally, in the present specification, a signal obtained through a Hartmann plate required for measuring an optical characteristic of an eye to be measured is made a first signal, and a signal obtained through a Placido's disk required for measuring a corneal shape of the eye to be measured is made a second signal.
However, in the conventional eye characteristic measuring apparatus, a processing has been performed such that a coordinate of the measuring apparatus itself, for example, the center of a light receiving part is made the origin of coordinates. Thus, according to such a coordinate system, for example, in a surgical apparatus, there is a case where measurement data is not fully related to the eye, and it is not necessarily suitable. Besides, as a conventional measuring apparatus, there is an apparatus called a photo-refract meter for obtaining the refractive power of a subject eye and a corneal shape, however, a display is not necessarily carried out in the same coordinate system.
In general, at a point of time when an alignment is adjusted manually or automatically, a measurement is started manually or automatically, however, a coordinate system (CCD coordinate) attached to a CCD at the time of the measurement corresponds to a CCD coordinate of an object side (eye side) opposite to the CCD through a lens. Although a measurement with a Hartmann wavefront sensor (first measurement system) and a corneal shape measurement (second measurement system) are substantially simultaneously performed in the respective CCDs, there is a case where the measurements are performed at times which are not identical strictly. Thus, for example, the eye is moved in the measurement, which becomes a main cause, and there is no guarantee that the CCD coordinate system of the first measurement system becomes identical to the CCD coordinate of the second measurement system. Besides, it is already performed to obtain a pupil edge from an anterior eye image and to use it for alignment. However, in the case where the acquisition timing of a Hartmann image is not completely coincident with the acquisition timing of the alignment image of the anterior eye part, if the alignment is made by only the alignment image of the anterior eye part, there is a possibility that a deviation occurs in the alignment of the Hartmann measurement by the movement of an eye or the like.
Further, in recent years, in an orthokeratology surgical operation, there has arisen a request to superimpose optical characteristic measurement data, such as aberrations of the subject eye or refractive power data, obtained from a first light receiving part as an eye optical characteristic measurement system upon corneal topography measurement data, such as corneal data of the subject eye, obtained from a second light receiving part as a corneal topography measurement system.
Besides, in the convention optical characteristic measuring apparatus, a case is conceivable in which it is difficult to simultaneously measure the optical characteristic of the subject eye and the corneal shape.
In view of the above, an object of the invention is to provide an eye characteristic measuring apparatus which correlates the aberrations of a subject eye or refractive power data obtained from a first light receiving part with corneal data of the subject eye obtained from a second light receiving part so that they can be precisely superimposed. Besides, an object of the invention is to match coordinates of a corneal shape measurement and a wavefront measurement using the same image as an alignment system by graphically comparing pupils of both to make positions coincident with each other, or to correlate a coordinate system of the alignment system with a coordinate system of the wavefront measurement.
Further, an object of the invention is to provide a structure adequate to capture a first signal of a first measurement system and a second signal of a second measurement system simultaneously or substantially simultaneously. Besides, an object of the invention is to provide a structure adequate to continuously capture a first signal and a second signal simultaneously or substantially simultaneously. Besides, an object of the invention is to perform a measurement when a first signal and a second signal are put into a state suitable for the measurement. Besides, an object of the invention is to perform a measurement in such a state that when there are plural factors exerting influences on the measurement, highly reliable measurement results can be obtained by judging the suitability of those factors by use of signals adequate to detect them and by deciding measuring timings.